Recording medium, image processing method, and information terminal

ABSTRACT

An information terminal includes acquiring an image of a first subject that is captured by a first sensor provided on a back surface of a surface on which a screen of the information terminal is disposed, and when displaying the image on the screen, changing a degree of scaling up/down of the image and a position at which the image is displayed in accordance with a position of a second subject that is imaged by a second sensor provided to the information terminal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of

International Application PCT/JP2013/062431 filed on Apr. 26, 2013 anddesignating the U.S., the entire contents of which are incorporatedherein by reference.

FIELD

The present invention relates to an image processing program, an imageprocessing method, and an information terminal.

BACKGROUND

With increasing awareness of information security, biometrics are beingintroduced for authentication for unlocking of and login in personalinformation terminals, such as smartphones, slate terminals, and tabletterminals.

When a living body is imaged with an information terminal, if theposition or posture of a part of the living body that is a subject isnot proper, a disadvantage that it would not be possible to correctlyextract biological information used for authentication or the extractedamount of characteristics would not match the registered amount ofcharacteristics may occur. In such a case, the time for authenticationextends and furthermore the accuracy of authentication lowers.

As an exemplary technology to deal with the problem, there is atechnology for displaying an operation instruction for positioning andguiding a part of a living body such that the operation instruction issuperimposed onto an image of the living body that is acquired by asensor.

Patent Document 1: Japanese National Publication of International PatentApplication No. 2010-541046

Patent Document 2: Japanese Laid-open Patent Publication No. 2007-052534

Patent Document 3: Japanese Laid-open Patent Publication No. 2009-157908

Patent Document 4: Japanese Laid-open Patent Publication No. 2004-258714

Patent Document 5: Japanese Laid-open Patent Publication No. 2008-071030

The above-described technology, however, has a limit to improvement ofaccuracy of authentication as described below.

For example, from among information terminals, such as smartphones,slate terminals, and tablet terminals, there are terminals in each ofwhich a sensor that images a living body is disposed on the backsurface, i.e., on the back of the screen. When such an informationterminal images a living body, because it is not possible for a user todirectly view the position of the sensor, it is more difficult todispose a part of the living body in an appropriate location. In each ofthe above-described technologies, however, an operation instruction forpositioning or guiding the part of the living body is only issued on anassumption that the sensor is set in a position that the user candirectly view and thus it is not possible to apply such positioning andguiding to a case where the sensor is on the back surface. For thisreason, it is not possible, with the above-described technologies, tosolve the disadvantage that biological information used forauthentication is not necessarily extracted or the amount of extractedcharacteristics does not necessarily match the registered amount ofcharacteristics, which may lower the accuracy of authentication.

SUMMARY

According to an aspect of the embodiment of the invention, anon-transitory computer readable recording medium stores therein animage processing program that causes an information terminal to executea process including: acquiring an image of a first subject that iscaptured by a first sensor provided on a back surface of a surface onwhich a screen of the information terminal is disposed; and whendisplaying the image on the screen, changing a degree of scaling up/downof the image and a position at which the image is displayed inaccordance with a position of a second subject that is imaged by asecond sensor provided to the information terminal.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a functional configuration of aninformation terminal according to a first embodiment.

FIG. 2 is a diagram illustrating an exemplary method of determining adisplay area of a palm image.

FIG. 3 is a diagram illustrating the exemplary method of determining adisplay area of a palm image.

FIG. 4 is a diagram illustrating an exemplary palm image displayed on atouch panel.

FIG. 5 is a diagram illustrating an exemplary palm image displayed onthe touch panel.

FIG. 6 is a diagram illustrating an exemplary palm image displayed onthe touch panel.

FIG. 7 is a flowchart illustrating a procedure of authenticationprocessing according to the first embodiment.

FIG. 8 is a block diagram illustrating a functional configuration of aninformation terminal according to a second embodiment.

FIG. 9 is a flowchart illustrating a procedure of authenticationprocessing according to the second embodiment.

FIG. 10 is a block diagram illustrating a functional configuration of aninformation terminal according to a third embodiment.

FIG. 11 is a flowchart illustrating a procedure of authenticationprocessing according to the third embodiment.

FIG. 12 is a diagram for explaining an exemplary computer that executesan image processing programs according to the first to thirdembodiments.

DESCRIPTION OF EMBODIMENTS

The image processing program, the image processing method, and theinformation terminal according to the present application will bedescribed below with reference to the accompanying drawings. Theembodiments do not limit the disclosed technology. Each embodiment canbe combined as appropriate within a range in which there is nocontradiction between the contents of processing.

First Embodiment

[Configuration of Information Terminal]

First, a functional configuration of an information terminal accordingto an embodiment will be described. FIG. 1 is a block diagramillustrating a functional configuration of an information terminalaccording to a first embodiment. The information terminal 10 representedin FIG. 1 is a terminal device that performs information processing. Forthe example illustrated in FIG. 1, the following descriptions will begiven with an assumption that palm vein authentication is employed forauthentication for unlocking of the screen of the information terminal10, i.e., the screen, or login.

When causing a vein sensor 13 that is disposed on the back of the screento image the palm, the information terminal 10 displays the imagecaptured by the vein sensor 13 as the sight for positioning the palm onthe screen. As part of such positioning, the information terminal 10performs image processing for changing the position and size of theimage displayed on the screen in accordance with the position of anorgan of the face, e.g., the position of an eye, in the image capturedby a camera 12 provided on the side of the screen. The palm is coveredby a mode of a first subject. The face is covered by a second subject.

According to a mode, the information terminal 10 can be implemented byinstalling an image processing program that is provided as packagesoftware or online software in a desired computer. For example, theimage processing program is installed in, not only mobile communicationterminals, such as smartphones, mobile phones, or personal handyphonesystems (PHS), but also tablet terminals and slate terminals includingpersonal digital assistants (PDA) not connecting to a mobilecommunication network. Accordingly, the tablet terminals and slateterminals can function as the information terminal 10. Tablet terminalsand slate terminals are exemplified here as an example by which theinformation terminal 10 is implemented. Alternatively, the imageprocessing program may be installed in a fixed terminal, such as apersonal computer.

As illustrated in FIG. 1, the information terminal 10 includes a touchpanel 11, the camera 12, the vein sensor 13, a distance sensor 14, aproper disposition storage unit 15, a viewpoint detector 16, a displaycontroller 17, and an authentication unit 18. The information terminal10 may include, in addition to the function units represented in FIG. 1,various function units that known tablet terminals and slate terminalsinclude. For example, when the information terminal 10 is implemented asa mobile communication terminal, the information terminal 10 may furtherinclude function units, such as a radio communication unit and a globalpositioning system (GPS) receiver, that communicate via an antenna and amobile communication network.

The touch panel 11 is a device that is capable of displaying and onwhich inputs can be made. According to a mode, the touch panel 11displays an image that is output by an operation system (OS) and theapplication program. As another mode, the touch panel 11 receives atouching operation, such as tap, flick, sweep, pinch-in, or pinch-outmade on the screen.

The camera 12 is an imaging device on which an image sensor, such as acharge coupled device (CCD) or a complementary metal oxide semiconductor(CMOS), is mounted. For example, on the camera 12, three or more typesof light receiving elements for, for example, red (R), green (G), andblue (B) can be mounted. As an example of implementation of the camera12, an in-camera that is provided to the same surface as that of thescreen of, for example, a tablet terminal or a slate terminal can beappropriated. The case where the information terminal 10 includes thecamera 12 is exemplified here; however, the information terminal 10 doesnot necessarily include the camera 12 if an image can be acquired via anetwork or a storage device.

For example, the camera 12 starts imaging in response to a touchingoperation corresponding to a command for, for example, authenticationfor screen unlocking or log-in on the touch panel 11. The imaging areaof the camera 12 provided to the side of the screen of the informationterminal 10 covers, in addition to the face of the user of theinformation terminal 10 that views the display on the screen, the neck,the cloth, etc. Accordingly, the image captured by the camera 12contains, in addition to the face of the user of the informationterminal 10, the neck, the cloth, etc. An image that is captured by thecamera 12 can be referred to as a “face image” below.

The vein sensor 13 is a sensor that captures a blood-vessel pattern ofveins that are inside the palm. According to a mode, the vein sensor 13is configured by including an illuminator that emits near infrared lightand an imaging device including an image sensor capable of capturing thenear infrared light. For example, for the imaging device, an out-camerathat is provided on the back of the screen of a tablet terminal or aslate terminal can be appropriated.

The vein sensor 13 is provided near the end of the information terminal10. For example, if the information terminal 10 has a rectangularhousing, the vein sensor 13 is provided on the opposite surface to thesurface on which the screen is set, i.e., on the back, and near any oneof the four corners of the housing. For this reason, when the palm isdisposed in an appropriate size at the center of the imaging area of thevein sensor 13, the user who holds his/her hand up to the vein sensor 13on the back of the screen while looking at the display on the screen mayview part of his/her fingers protruding over the screen.

In response to, for example, a touch operation corresponding to acommand for authentication for screen unlocking or login on the touchpanel 11, the vein sensor 13 starts imaging. In other words, the veinsensor 13 emits near infrared light from the illuminator. Accordingly,the vein sensor 13 gathers, on the imaging device that is started inassociation with the emission of the infrared light from theilluminator, the reflected light that is the infrared light havingreflected from the surface or the inside of the palm. As a result,photoelectric conversion on the reflected light gathered on the imagingdevice is performed and thus an image of the subject within the imagingarea of the imaging device is output. When the imaging area covers thepalm, the hemoglobin in the veins absorbs the near infrared light, whichmakes it possible to acquire an image in which the blood vessel patternof the veins is enhanced. An image that is captured by the vein sensor13 can be referred to as a “palm image” below. It is here assumed thatthe palm serves as a part containing veins by which authentication isperformed. Alternatively, the back of the hand may serve as a part bywhich authentication is performed.

As described above, to perform authentication for screen unlocking orlogin, the two imaging devices, i.e., both the camera 12 and the veinsensor 13 according to the embodiment, are started to capture imagesrespectively. In this case, images are captured in synchronizationbetween the camera 12 and the vein sensor 13. For example, both of theframe of the palm image captured by the vein sensor 13 and the frame ofthe face image captured by the camera 12 are associated with each otherby using, for example, a frame number. Such association makes itpossible to use the images of the same frame number in the followingprocessing as the images captured at the same time point. Capturing theface image and the palm image is different from a normal use in which,in a normal information terminal, one of cameras is started according toswitching between imaging modes and the camera is exclusively used whilethe other camera stops.

As a trigger for starting capturing of a palm image, a tap operation forauthentication for unlocking or login is exemplified here; however, thetrigger is not limited to this example. For example, imaging may bestarted by an operation on a physical key, such as a button (notrepresented). Alternatively, the camera 12 and the vein sensor 13 may bestarted without any specific trigger and, when a certain gesture, suchas a wink or a V-sign, is detected from an image that is captured by anyone of the imaging devices, positioning of the palm may be started.

The distance sensor 14 is a sensor that measures the distance betweentwo points. According to a mode, the distance sensor 14 sends wavemotions, such as infrared rays, radio waves, or ultrasonic waves, towarda direction indicated by the viewpoint detector 16, which will bedescribed below, i.e., a direction corresponding to the position atwhich the point of view is detected on the face image. Moreover, thedistance sensor 14 receives the wave motions that have reflected on thesubject and, by calculating the time difference or the phase differencebetween the sent wave motions and the received wave motions, measuresthe distance between the distance sensor 14 and the viewpoint.

The proper disposition storage unit 15 is a storage unit that storesproper disposition of a living body with respect to the vein sensor 13.The “proper disposition” denotes a disposition in which, when the userin a standard posture in which the user uses the information terminal 10holds his/her palm up to the vein sensor, part of the hand is exposedand viewed over the screen. For example, there is a disposition inwhich, when the user of the information terminal 10 holds theinformation terminal 10 with one of his/her hands and holds his/her palmup to the vein sensor 13 in a posture in which the user stretches thefingers of the other hand while looking at the display on the screen,the tips of the thumb, index finger, middle finger, and ring finger areexposed and viewed over the screen.

The such disposition is employed for disposing the palm at the center ofthe imaging area of the vein sensor 13 that is set near the corner ofthe information terminal and for the following purpose: for, by exposingthe fingertips when imaging the palm of the hand opposite to the handholding the information terminal 10, allowing the user of theinformation terminal 10 to know how much the vein sensor 13 and the palmare distant from each other.

The distance between the vein sensor 13 and the palm that is determinedas proper is determined according to the performance of equipment of thevein sensor 13, such as, in addition to the resolution of the imagesensor, the number and type of lenses. It is here assumed that a palmimage captured in the same environment as the proper disposition isregistered not only when imaging is performed when the palm veinauthentication performed, but also when a palm image of the owner of theinformation terminal 10 is previously registered. A palm image that ispreviously registered to be matched with a palm image captured by thevein sensor 13 can be referred to as a “registered palm image” below.

According to a mode, the proper disposition storage unit 15 storesspecifying information with which it is possible to specify a rectangleobtained by modeling the surface of the palm that is held up to the veinsensor 13, such as three-dimensional coordinates of vertices forming arectangle, or three-dimensional coordinates of the center of gravity ofthe rectangle, and the height and width of the rectangle. For thecoordinates, for example, relative coordinates with respect to theinformation terminal 10 are used. The case where the disposition of thepalm with respect to the vein sensor 13 is modelled in a rectangle hasbeen exemplified; however, any shape, such as an oval, circle, orpolygon may be used for modelling.

The viewpoint detector 16 is a processor that detects the position ofthe point of view of the user of the information terminal 10. Accordingto a mode, the viewpoint detector 16 performs image processing, such asskin color detection and template matching, on a face image that iscaptured by the camera 12. For example, by detecting the skin color fromthe face image, the viewpoint detector 16 extracts the face partcontained in the face image. Moreover, by performing template matchingon the face area that is extracted by the skin color detection, theviewpoint detector 16 extracts geometrical characteristics, such as theshape and size of organs of the face, such as the eyes, nose, mouth andears, from the face part image. Accordingly, the positions of the righteye, left eye, or both the right and left eyes on the face image arespecified.

After specifying the position of the eye on the face image, theviewpoint detector 16 causes the distance sensor 14 to send wave motionsin the direction corresponding to the position of the eye on the faceimage to cause the distance sensor 14 to measure the distance betweenthe distance sensor 14 and the eye of the user of the informationterminal 10. The direction in which the distance sensor 14 is caused tosend wave motions may be the direction corresponding to the center ofthe right eye on the face image or the direction corresponding to thecenter of the left eye, or the direction corresponding to the middlepoint between the eyes. Thereafter, the viewpoint detector 16 calculatesthe coordinates in a three-dimensional space at which the eye of theuser of the information terminal 10 positions, i.e., the position of theviewpoint, from the distance to the eye of the user of the informationterminal 10 measured by the distance sensor 14, the previously-detectedposition of the eye on the face image, and the coordinates of thedistance sensor 14.

The display controller 17 is a processor that performs display controlon the touch panel 11. According to a mode, the display controller 17determines the size and position of the palm image captured by the veinsensor 13 and to be displayed on the touch panel 11 from the position ofthe viewpoint detected by the viewpoint detector 16 and the properdisposition of the palm stored in the proper disposition storage unit15.

FIGS. 2 and 3 are diagrams illustrating an exemplary method ofdetermining a display area of a palm image. FIG. 2 illustrates a sideview of the screen of the information terminal 10 when viewed from itsside surface, and FIG. 3 illustrates an oblique view of the screen ofthe information terminal 10 when viewed obliquely. FIG. 3 does notillustrate the camera 12 and the vein sensor 13.

As illustrated in FIG. 2, when a viewpoint 200 and each of the verticescontained in the rectangular proper disposition 210 are connected with aline segment, the position and size of a display area 220 projected ontothe screen of the touch panel 11 are determined as a display positionand a display size. For example, as illustrated in FIG. 3, the positionand size displayed on the touch panel 11 are defined by the fourintersections 220A to 220D corresponding to the line segments.

The intersection 220A represents the point at which the line segmentconnecting the viewpoint 200 and the vertex 210A intersects with thescreen of the touch panel 11 and the intersection 220B represents thepoint at which the line segment connecting the viewpoint 200 and thevertex 210B intersects with the screen of the touch panel 11. Theintersection 220C represents the point at which the line segmentconnecting the viewpoint 200 and the vertex 210C intersects with thescreen of the touch panel 11, and the intersection 220D denotes thepoint at which the line segment connecting the viewpoint 200 and thevertex 210D intersects with the screen of the touch panel 11.

As described above, the display controller 17 determines, per straightline connecting the viewpoint detected by the viewpoint detector 16 anda vertex contained in the proper disposition stored in the properdisposition storage unit 15, the display area 220 of the palm image bycalculating the coordinates of the intersection at which the straightline intersects with the screen of the touch panel 11. The position andsize of the display area 220 is determined according to the dispositionof the four intersections 220A to 220D. For example, the closer to thescreen the viewpoint 200 is, the smaller the size of the display area220 is. The more the viewpoint is distant from the screen, the closer tothe size of the proper disposition 210 the size of the display area 220is.

Moreover, the display controller 17 displays the palm image captured bythe vein sensor 13 in accordance with the pre-determined displayposition and display size on the touch panel 11. For example, accordingto the example illustrated in FIGS. 2 and 3, the palm image captured bythe vein sensor 13 is displayed on the display area 220 containing theintersections 220A to 220D.

FIGS. 4 to 6 are diagrams illustrating exemplary palm images displayedon the touch panel 11. FIG. 4 illustrates a mode in which the palm isheld up at the position matching the proper disposition 210. When thepalm is held up at the position at which the palm matches the properdisposition 210, the ends of fingers in the palm image displayed on thetouch panel 11 and the real fingertips exposed over the screen arenaturally viewed as if they are connected. Such display of the palmimage allows the user of the information terminal 10 to check acircumstance that the palm is presented at the proper position andaccordingly the user can hold his/her palm at the current presentationposition until the palm vein authentication ends.

FIG. 5 illustrates a mode in which the palm is held up at a positioncloser to the screen than the proper disposition 210 is. When the palmis held up at a position closer to the screen than the properdisposition 210 is as described above, the scale of the palm includingthe fingers in the palm image displayed on the touch panel 11 isdisplayed greater than the scale of the real fingertips exposed over thescreen. This results from the fact that a wide-angle lens is provided tothe vein sensor 13 in many cases because the distance from the veinsensor 13 to the fingertips is shorter than the distance from theviewpoint of the user of the information terminal 10 to the fingertips.For this reason, even when the palm gets closer to the screen than theproper disposition 210 is so slightly that it is difficult for the userwho looks at the fingertips over the screen to see it is closer than theproper disposition, it is possible to display the palm image in whichthe palm and the fingertips are imaged in a scale larger than the scaleof the real fingertips viewed over the screen. Such display of the palmimage allows the user of the information terminal 10 to check acircumstance that the palm is presented closer than the proper positionis and accordingly to determine that it is preferable to present thepalm more apart from the housing of the information terminal 10 than thecurrent presentation position is.

FIG. 6 illustrates a mode where the palm is held up in a position moreapart from the screen than the proper disposition 210 is. When the palmis held up at a position more apart from the screen than the properdisposition 210 is as described above, the scale of the palm includingthe fingers in the palm image displayed on the touch panel 11 isdisplayed smaller than the scale of the real fingers exposed over thescreen. For this reason, even when the palm becomes more distant fromthe screen than the proper disposition 210 is so slightly that it isdifficult for the user who looks at the fingertips over the screen tosee it is closer than the proper disposition, it is possible to displaythe palm image in which the palm and the fingertips are imaged in ascale smaller than the scale of the real fingertips viewed over thescreen. Such display of the palm image allows the user of theinformation terminal 10 to check a circumstance that the palm ispresented more distant than the proper position is and accordingly todetermine that it is preferable to present the palm closer to thehousing of the information terminal 10 than the current presentationposition is.

Furthermore, according to the examples illustrated in FIGS. 4 to 6,different from the display of the palm image in front of the viewpointof the user of the information terminal 10, the palm image is displayedin the direction, shifted from the right front, toward the properdisposition from the viewpoint of the user of the information terminal10. For this reason, the user of the information terminal 10 can alsopresent the palm while intuitively knowing the field of view of the veinsensor 13 that is set on the back of the screen and thus is difficult toview. Furthermore, as illustrated in FIGS. 4 to 6, by displaying thecenter position of the area from which a pattern of blood vessels insidethe palm is extracted such that the center position is superimposed ontothe palm image, it is possible to position the palm by using the centerposition as the sight.

Descriptions will be given again for FIG. 1. The authentication unit 18is a processor that performs palm vein authentication. According to amode, the authentication unit 18 extracts an amount of characteristicson the blood vessel pattern of veins from the palm image captured by thevein sensor 13. For example, the authentication unit 18 takes out theblood vessel part from the palm image, thins the blood vessel part, andextracts, as vein data, the amounts of characteristics, such as thecoordinates of a junction in the blood vessels, the length betweenjunctions, and the junction angle of a junction. Moreover, theauthentication unit 18 calculates a matching score between the vein dataextracted from the palm image and the pre-registered vein data on, forexample, the owner of the information terminal 10. By registeringmultiple sets of vein data on persons permitted to use the informationterminal 10, it is possible to perform, in addition to 1:1authentication, 1:N authentication. When the highest matching score fromamong the pre-calculated matching scores is equal to or larger than agiven threshold, the authentication unit 18 determines that the palmvein authentication succeeded. When the highest matching score is lessthan the given threshold, the authentication unit 18 determines that thepalm vein authentication failed. The authentication result fromperforming of the palm vein authentication by the authentication unit 18described above is output to the OS that performs authentication forunlocking or login and the application program. The authentication unit18 can employ any matching method, such as a minutia method, a patternmatching method, or a frequency analysis method.

The authentication unit 18 does not necessarily perform palm veinauthentication soon after a palm image is captured by the vein sensor13. In other words, each time the vein sensor 13 captures a palm image,the authentication unit 18 determines whether the palm in the palm imageis disposed at a proper position. For example, the authentication unit18 can perform palm vein authentication when the difference between thediameter of a finger in the palm image captured by the vein sensor 13and the diameter of the finger of the pre-registered vein data is equalto or smaller than a given threshold. The authentication unit 18 canalso perform the palm vein authentication when receiving an input of agiven audio message, such as “OK”, from the user of the informationterminal 10. Even when the authentication unit 18 fails in the palm veinauthentication, it is possible to display the palm image on the touchpanel 11 by using the display controller 17 and retry the palm veinauthentication until the number of times of retry reaches a given numberof times.

It is possible to implement the above-described viewpoint detector 16,the display controller 17, and the authentication unit 18 by causing acentral processing unit (CPU) or a micro processing unit (MPU) toexecute the image processing program. The above-described function unitsmay be implemented by using a hard wired logic, such as an applicationspecific integrated circuit (ASIC) or a field programmable gate array(FPGA).

For the above-described proper disposition storage unit 15, asemiconductor memory device or a storage device can be used. Forexample, as exemplary semiconductor memory devices, there are a videorandom access memory (VRAM), a random access memory (RAM), a read onlymemory (ROM), and a flash memory. Furthermore, as an exemplary storagedevice, there is a storage device, such as a hard disk or an opticaldisk.

[Flow of Processing]

FIG. 7 is a flowchart illustrating a procedure of the authenticationprocessing according to the first embodiment.

The authentication processing starts, for example, when a touchoperation corresponding to a command for authentication for screenunlocking or login authentication is performed on the touch panel 11.

As illustrated in FIG. 7, when the camera 12 captures a face image andthe vein sensor 13 captures a palm image (step S101), the viewpointdetector 16 detects the position of an eye of a user on the face imagecaptured at step S101 (step S102).

By causing the distance sensor 14 to send wave motions to the directioncorresponding to the position of the eye on the face image detected atstep S102, the viewpoint detector 16 causes the distance sensor 14 tomeasure the distance between the distance sensor 14 and the eye of theuser of the information terminal 10 (step S103).

From the distance to the eye of the user of the information terminal 10measured at step S103, the position of the eye on the face imagedetected at step S102, and the coordinates of the distance sensor 14,the viewpoint detector 16 then calculates the coordinates in athree-dimensional space at which the eye of the user of the informationterminal 10 positions, i.e., the position of the viewpoint (step S104).

The display controller 17 reads a proper disposition stored in theproper disposition storage unit 15 (step S105). Thereafter, the displaycontroller 17 determines a display area of the palm image, i.e., thedisplay position and the display size, by calculating, per straight lineconnecting the viewpoint detected at step S104 and a vertex contained inthe proper disposition read at step S105, the coordinates of theintersection between the straight line and the screen (step S106).

The display controller 17 displays, on the touch panel 11, the palmimage that is captured at step S101 in accordance with the displayposition and the display size that are determined at step S106 (stepS107).

The processing of steps S101 to S107 is repeatedly performed until theauthentication unit 18 determines that the palm contained in the palmimage is disposed at a proper position (NO at step S108).

Thereafter, when the palm contained in the palm image is disposed in aproper position (YES at step S108), the authentication unit 18 performsthe following processing: the authentication unit 18 performs palm veinauthentication by matching vein data extracted from the palm imagecaptured at step S101 and pre-registered vein data (step S109), outputsthe authentication result to an OS or an application program running onthe information terminal 10, and ends the processing.

[Effect of First Embodiment]

As described above, in the information terminal 10 according to theembodiment, when the vein sensor 13 that is set at the back of thescreen images the palm, the position and size of the palm image to bedisplayed on the screen are changed in accordance with the position ofthe eye imaged on the camera 12 that is set at the same surface as thatof the screen. For example, when part of the hand, i.e., fingertips, isexposed over the screen, it is possible to perform positioning such thatthe palm is positioned at the center of the palm image and the scale ofthe palm and fingers in the palm image matches the scale of the exposedreal fingers. For this reason, according to the information terminal 10according to the embodiment, even when the vein sensor 13 is set at theback of the screen, it is possible to increase the positioning accuracy.Thus, the information terminal 10 according to the embodiment canimprove the authentication accuracy.

Second Embodiment

For the first embodiment, the case has been exemplified where thedistance sensor 14 is used to detect the position of the viewpoint ofthe user of the information terminal 10; however, the distance sensor 14is not necessarily included depending on the type of the informationterminal. For the second embodiment, an information terminal 20 thatestimates the position of the viewpoint of a user without the distancesensor 14 will be described below.

FIG. 8 is a block diagram illustrating a functional configuration of theinformation terminal 20 according to a second embodiment. Theinformation terminal 20 is different from the information terminal 10represented in FIG. 1 in that the information terminal 20 includes adistance storage unit 21 and a viewpoint position estimation unit 22. InFIG. 8, processing units different in function from those of theinformation terminal 10 represented in FIG. 1 are denoted with differentnumerals, and processing units having the same functions as those of theinformation terminal 10 are denoted by the same reference numerals andthe descriptions thereof will be omitted.

The distance storage unit 21 is a storage unit that stores the distancesto the information terminal 20. According to a mode, the distancestorage unit 21 stores data in which the number of pixels forming thewidth of the face on a face image, from imaging of a standard person bythe camera 12, and the distance measured between the face of thestandard person and the information terminal 20 are associated with eachother. The “standard person” refers to, for example, a person whosewidth of the face is statistically an average or a median. The casewhere the width of the face and the distance to the information terminal20 are stored in association with each other has been exemplified;however, it suffices if the distance between characteristic points isused, and the length of the face, or the distance between the left andright eyes, and the distance to the information terminal 20 may bestored in association with each other. The case has been exemplifiedwhere the width of the face on the face image and the measured distancefrom the imaging of the standard person by the camera 12 are stored.Alternatively, the width of the face and the measured distance fromimaging of the owner of the information terminal 20 by the camera 12 maybe previously acquired.

While the viewpoint position estimation unit 22 is common with theviewpoint detector 16 represented in FIG. 1 in the processing untilspecifying of the position of the right eye, the left eye, or the rightand left eyes on the face image, they are different with respect to thesubsequent processing. Specifically, the viewpoint position estimationunit 22 reads the width of the imaged face of the standard person andthe measured distance to the information terminal 20 from the distancestorage unit 21. The viewpoint position estimation unit 22 counts thenumber of pixels forming the width of the face of the user of theinformation terminal 20 from a face image captured by the camera 12, byperforming image processing, such as skin color detection or templatematching. The viewpoint position estimation unit 22 then calculates aratio between the width of the face of the user of the informationterminal 20, for which the number of pixels is counted from the faceimage, and the number of pixels of the width of the face on the faceimage from imaging of a standard person by the camera 12, e.g., thequotient obtained by dividing the former width by the latter width.Moreover, the viewpoint position estimation unit 22 calculates thedistance between the face of the user of the information terminal 20 andthe information terminal 20 by multiplying the measured distance betweenthe face of the standard person and the information terminal 20, whichis read from the distance storage unit 21, by an inverse of thepreviously-calculated ratio, i.e., an inverse of the quotient.

Accordingly, it is possible to regard the width of the face of the userof the information terminal 20 as the width of the standard person and,in accordance with the scaling up/down of the width of the face obtainedby this capturing of the face image, correct the measured distance fromprevious imaging of the standard person. For example, when the user ofthe information terminal 20 keeps his/her face closer to the screen thanthe face of the previously-imaged standard person was, the width of theface of the user is detected in a larger scale. In this case, becausethe above-described ratio is calculated to be greater than 1, it ispossible to correct the measured distance, from previous imaging of thestandard person, to be smaller by multiplying the measured distance bythe inverse of the ratio. On the other hand, when the user of theinformation terminal 20 keeps his/her face more away from the screenthan the previously-imaged face of the standard person was, the width ofthe face of the user is detected in a smaller scale. In this case,because the above-described ratio is calculated to be smaller than 1, itis possible to correct the measured distance, from previous imaging ofthe standard person, to be greater by multiplying the measured distanceby the inverse of the ratio. Here, the case has been exemplified wherethe ratio is calculated. Alternatively, the difference between thewidths may be calculated. For example, it suffices if, while themeasured distance is corrected to be greater when the width of the faceof the user of the information terminal 20 is smaller than the width ofthe previously-imaged face of the standard person, the measured distanceis corrected to be smaller when the width of the face of the user of theinformation terminal 20 is larger than the width of thepreviously-imaged face of the standard person.

Thereafter, from the previously-estimated distance to the face of theuser of the information terminal 20, the previously-detected position ofthe eye on the face image, and the coordinates of the informationterminal 20, e.g., the coordinates of the center of gravity of thescreen, the viewpoint position estimation unit 22 estimates thecoordinates in a three-dimensional space at which the eye of the user ofthe information terminal 20 positions, i.e., the position of theviewpoint.

FIG. 9 is a flowchart illustrating a procedure of authenticationprocessing according to the second embodiment. As in the case of theflowchart illustrated in FIG. 7, the authentication processing statswhen a touch operation corresponding to a command for authentication forscreen unlocking or login is performed on the touch panel 11.

As illustrated in FIG. 9, when the camera 12 captures a face image andthe vein sensor 13 captures a palm image (step S101), the viewpointposition estimation unit 22 detects the position of an eye of a user onthe face image captured at step S101 (step S102).

By performing image processing, such as skin color detection or templatematching, the viewpoint position estimation unit 22 counts the number ofpixels forming the width of the face of the user of the informationterminal 20 from the face image captured at step S101 (step S201).

Using the ratio between the number of pixels of the width of the facecounted at step S201 and the number of pixels of the width of the faceon a face image stored in the distance storage unit 21, the viewpointposition estimation unit 22 then estimates the distance between the faceof the user of the information terminal 20 and the information terminal20 by correcting the measured distance between the face of a standardperson and the information terminal 20 stored in the distance storageunit 21 (step S202).

Thereafter, from the distance to the eye of the user of the informationterminal 20 estimated at step S202, the position of the eye on the faceimage detected at step S102, and the coordinates of the informationterminal 20, the viewpoint position estimation unit 22 calculates thecoordinates in a three-dimensional space at which the eye of the user ofthe information terminal 20 positions, i.e., the position of theviewpoint (step S203).

The display controller 17 reads a proper disposition stored in theproper disposition storage unit 15 (step S105). Thereafter, the displaycontroller 17 determines a display area of the palm image, i.e., thedisplay position and display size, by calculating, per straight lineconnecting the viewpoint estimated at step S203 and a vertex containedin the proper disposition read at step S105, the coordinates of theintersection between the straight line and the screen (step S106).

The display controller 17 displays, on the touch panel 11, the palmimage captured at step S101 in accordance with the display position andthe display size that are determined at step S106 (step S107).

The processing of steps S101 to S107 is repeatedly performed until theauthentication unit 18 determines that the palm contained in the palmimage is disposed at a proper position (NO at step S108).

Thereafter, when the palm contained in the palm image is disposed in aproper position (YES at step S108), the authentication unit 18 performsthe following processing: the authentication unit 18 performs palm veinauthentication by matching vein data extracted from the palm imagecaptured at step S101 and pre-registered vein data (step S109), outputsthe authentication result to an OS or an application program running onthe information terminal 20, and ends the processing.

[Effect of Second Embodiment]

As described above, in the information terminal 20 according to thesecond embodiment, even when the vein sensor 13 is set at the back ofthe screen, it is possible to increase the positioning accuracy, whichimproves the authentication accuracy as according to the above-describedfirst embodiment.

Furthermore, because the width of the face of the user of theinformation terminal 20 is regarded as the width of the standard personand the measured distance from previous imaging of the standard personis corrected in accordance with the scaling up/down of the width of theface obtained by this capturing of the face image, the informationterminal 20 according to the second embodiment is capable of estimatingthe position of the viewpoint without hardware, such as the distancesensor 14.

Third Embodiment

For the second embodiment, the case has been exemplified where theposition of the viewpoint of the user of the information terminal 20 isestimated from the width of the face in the face image captured by thecamera 12; however, the width of the face is not necessarily used toestimate the position of the viewpoint. For the third embodiment, aninformation terminal 30 that estimates the position of the viewpoint ofa user by using a palm image captured by the vein sensor 13 will bedescribed below.

FIG. 10 is a block diagram illustrating a functional configuration ofthe information terminal 30 according to a third embodiment. Theinformation terminal 30 represented in FIG. 10 is different from theinformation terminal 20 represented in FIG. 8 in that the informationterminal 30 includes a distance storage unit 31 and a viewpoint positionestimation unit 32. In FIG. 10, processing units different in functionfrom those of the information terminal 20 represented in FIG. 8 aredenoted with different numerals, and processing units having the samefunctions as those of the information terminal 20 are denoted by thesame reference numerals and the descriptions thereof will be omitted.

The distance storage unit 31 is a storage unit that stores the distanceto the information terminal 30. According to a mode, the distancestorage unit 31 stores data in which the number of pixels forming thewidth of the palm on a palm image, from imaging of a standard person bythe vein sensor 13, and the distance between the face of the standardperson and the information terminal 30 are associated with each other.The “standard person” refers to, for example, a person whose width ofthe palm is statistically an average or a median. The case has beenexemplified where the width of the palm and the distance to theinformation terminal 30 are stored in association with each other.Alternatively, the height of the palm, or the lengths of fingers, andthe measured distance may be stored in association with each other. Thecase has been described where the width of the palm on the palm imageand the measured distance from the imaging of the standard person by thevein sensor 13 are stored. Alternatively, the width of the palm and themeasured distance from imaging of the owner of the information terminal30 by the vein sensor 13 may be previously acquired.

While the viewpoint position estimation unit 32 is common with theviewpoint position estimation unit 22 represented in FIG. 8 in theprocessing until specifying of the position of the right eye, the lefteye, or the right and left eyes on the face image, they are differentwith respect to the subsequent processing. Specifically, from thedistance storage unit 21, the viewpoint position estimation unit 32reads the width of the imaged palm of the standard person and themeasured distance to the information terminal 30. The viewpoint positionestimation unit 32 counts the number of pixels forming the width of thepalm of the user of the information terminal 30 from the palm imagecaptured by the vein sensor 13, by performing image processing, such asskin color detection or template matching. The viewpoint positionestimation unit 32 then calculates a ratio between the width of the palmof the user of the information terminal 30, for which the number ofpixels is counted from the palm image, and the number of pixels of thewidth of the palm on the palm image from imaging of a standard person bythe vein sensor 13, e.g., the quotient obtained by dividing the formerwidth by the latter width. Moreover, the viewpoint position estimationunit 32 calculates the distance between the face of the user of theinformation terminal 30 and the information terminal 30 by multiplyingthe measured distance between the face of the standard person and theinformation terminal 30, which is read from the distance storage unit31, by the previously-calculated ratio, i.e., the quotient.

Accordingly, because the width of the palm of the user of theinformation terminal 30 and the distance between the informationterminal 30 and the eye of the user of the information terminal 30derive from the physical constitution, they are regarded to beproportional to each other and the measured distance from previousimaging of the standard person can be corrected in accordance with thescaling up/down of the width of the palm obtained by this capturing ofthe palm image. For example, when the palm of the user of theinformation terminal 30 is larger than the palm of the previously-imagedstandard person, the width of the palm is detected in a larger scale. Inthis case, because the above-described ratio is calculated to be greaterthan 1, it is possible to correct the measured distance, from previousimaging of the standard person, to be greater by multiplying themeasured distance by the ratio. On the other hand, when the palm of theuser of the information terminal 30 is smaller than the palm of thepreviously-imaged standard person, the width of the palm is detected ina smaller scale. In this case, because the above-described ratio iscalculated to be smaller than 1, it is possible to correct the measureddistance, from previous imaging of the standard person, to be smaller bymultiplying the measured distance by the ratio. Here, the case has beendescribed where the ratio is calculated. Alternatively, the differencebetween the widths may be calculated. For example, it suffices if, whilethe measured distance is corrected to be smaller when the width of thepalm of the user of the information terminal 30 is smaller than thewidth of the previously-imaged palm of the standard person, the measureddistance is corrected to be greater when the width of the palm of theuser of the information terminal 30 is larger than the width of thepreviously-imaged palm of the standard person.

Thereafter, from the previously-estimated distance to the face of theuser of the information terminal 30, the previously-detected position ofthe eye on the face image, and the coordinates of the informationterminal 30, e.g., the coordinates of the center of gravity of thescreen, the viewpoint position estimation unit 32 estimates thecoordinates in a three-dimensional space at which the eye of the user ofthe information terminal 30 positions, i.e., the position of theviewpoint.

FIG. 11 is a flowchart illustrating a procedure of authenticationprocessing according to the third embodiment. As in the case of theflowchart illustrated in FIG. 7, the authentication processing statswhen a touch operation corresponding to a command for authentication forscreen unlocking or login is performed on the touch panel 11.

As illustrated in FIG. 11, when the camera 12 captures a face image andthe vein sensor 13 captures a palm image (step S101), the viewpointposition estimation unit 32 detects the position of an eye of a user onthe face image captured at step S101 (step S102).

By performing image processing, such as skin color detection or templatematching, the viewpoint position estimation unit 32 counts the number ofpixels forming the width of the palm of the user of the informationterminal 30 from the palm image captured at step S101 (step S301).

Using the ratio between the number of pixels of the width of the palmcounted at step S301 and the number of pixels of the width of the palmon the palm image stored in the distance storage unit 31, the viewpointposition estimation unit 32 then estimates the distance between the faceof the user of the information terminal 30 and the information terminal30 by correcting the measured distance between the face of the standardperson and the information terminal 30 stored in the distance storageunit 31 (step S302).

Thereafter, from the distance to the eye of the user of the informationterminal 30 estimated at step S302, the position of the eye on the faceimage detected at step S102, and the coordinates of the informationterminal 30, the viewpoint position estimation unit 32 estimates thecoordinates in a three-dimensional space at which the eye of the user ofthe information terminal 30 positions, i.e., the position of theviewpoint (step S303).

The display controller 17 reads a proper disposition stored in theproper disposition storage unit 15 (step S105). Thereafter, the displaycontroller 17 determines a display area of the palm image, i.e., thedisplay position and the display size, by calculating, per straight lineconnecting the viewpoint estimated at step S303 and a vertex containedin the proper disposition read at step S105, the coordinates of theintersection between the straight line and the screen (step S106).

The display controller 17 displays, on the touch panel 11, the palmimage captured at step S101 in accordance with the display position andthe display size that are determined at step S106 (step S107).

The processing of steps S101 to S107 is repeatedly performed until theauthentication unit 18 determines that the palm contained in the palmimage is disposed at a proper position (NO at step S108).

Thereafter, when the palm contained in the palm image is disposed in aproper position (YES at step S108), the authentication unit 18 performsthe following processing: the authentication unit 18 performs palm veinauthentication by matching vein data extracted from the palm imagecaptured at step S101 and pre-registered vein data (step S109), outputsthe authentication result to an

OS or an application program running on the information terminal 30, andends the processing.

Effect of Third Embodiment

As described above, in the information terminal 30 according to thethird embodiment, even when the vein sensor 13 is set at the back of thescreen, it is possible to increase the positioning accuracy, whichimproves the authentication accuracy as according to the above-describedfirst embodiment.

Furthermore, in the information terminal 30 according to the thirdembodiment, because the width of the palm of the user of the informationterminal 30 and the distance between the information terminal 30 and theeye of the user of the information terminal 30 are regarded to beproportional to each other, the measured distance from previous imagingof the standard person is corrected in accordance with the scalingup/down of the width of the palm obtained by this capturing of the palmimage. Thus, the information terminal 30 according to the thirdembodiment is capable of estimating the position of the viewpointwithout hardware, such as the distance sensor 14.

Fourth Embodiment

The embodiments of the disclosed apparatus have been described. Inaddition to the above-described embodiments, the present invention maybe carried out in various different modes. Other embodiments covered bythe invention will be described below.

[Substitute of Camera 12]

For the first to third embodiments, the case where the informationterminal 10, 20, or 30 includes the camera 12 is exemplified; however,the information terminal does not necessarily include the camera 12. Forexample, instead of detecting the position of an eye on the face image,it may be regarded that the viewpoint of the user of the informationterminal 10, 20, or 30 is on a given direction with respect theterminal, such as the normal line of the center of the screen, and thedirection in which the viewpoint positions with respect to theinformation terminal 10, 20, or 30 may be stored in, for example, aninternal memory. This enables detection or estimation of the viewpointeven if the camera 12 is not provided on the same surface as that of thescreen.

[Authentication System]

According to the first to third embodiments, the case has beenexemplified where the above-described image processing is performed whenpalm vein authentication is performed. The embodiments may be applied toa case where authentication other than the palm vein authentication isperformed. In other words, the above-described processing may besimilarly applied to a case where a device including a camera, a screen,and a sensor for authentication is between the position of an eye of auser and a part by which authentication is performed and the sensor forauthentication are apart from each other. For example, theabove-described processing, i.e., the processing illustrated in FIG. 7,FIG. 9, and FIG. 11, may be performed when an imaging device set on theback of the information terminal 10, 20, or 30 images the palm print,the back of the hand, or the palm shape (hand print) to perform palmprint authentication, back-hand authentication, or palm shapeauthentication.

The components of each device illustrated in the drawings are notnecessarily configured physically as illustrated in the drawings. Inother words, specific modes of distribution and integration of eachdevice are not limited to those illustrated in the drawings, and all orpart of the device may be configured by functional or physicaldistribution or integration per arbitrary unit in accordance withvarious loads or the usage. For example, the viewpoint detector 16 orthe display controller 17 may be connected as external devices of theinformation terminal 10 via a network. Alternatively, different devicesmay include the viewpoint detector 16 or the display controller 17,respectively, and they may cooperate via a network connection toimplement the functions of the information terminal 10.

[Image Processing Program]

The above-described various types of processing described for theabove-described embodiments can be implemented in a way that a computer,such as a personal computer or a work station, executes a preparedprogram. With reference to FIG. 12, an exemplary computer that executesthe image processing program with the same functions as those of theabove-described embodiments will be described below.

FIG. 12 is a diagram for explaining an exemplary computer that executesthe image processing programs according to the first to thirdembodiments. As illustrated in FIG. 12, a computer 100 includes anoperation unit 110 a, a speaker 110 b, a camera 110 c, a display 120,and a communication unit 130. The computer 100 further includes a CPU150, a ROM 160, a HDD 170, and a RAM 180. The units 110 to 180 areconnected via a bus 140.

As illustrated in FIG. 12, an image processing program 170 a thatimplements the same functions as those of the viewpoint detector 16 andthe display controller 17 illustrated in the first embodiment ispreviously stored in the HDD 170. Alternatively, the image processingprogram 170 a that implements the same functions as those of theviewpoint position estimation unit 22 and the display controller 17illustrated in the second embodiment may be previously stored in the HDD170. Alternatively, the image processing program 170 a that implementsthe same functions as those of the viewpoint position estimation unit 32and the display controller 17 illustrated in the third embodiment may bepreviously stored in the HDD 170. Integration or distribution of theimage processing program 170 a may be performed as appropriate as thatof the components of the functions units represented in FIGS. 1, 8, and10 may be. In other words, all data stored in the HDD 17 is notnecessarily stored in the HDD 170, and it suffices if only data neededfor processing is stored in the HDD 170.

The CPU 150 reads the image processing program 170 a from the HDD 170and loads the image processing program 170 a in the RAM 180.Accordingly, as illustrated in FIG. 12, the image processing program 170a functions as an image processing process 180 a. The image processingprocess 180 a properly loads various types of data read from the HDD 170in an area allocated to the image processing process 180 a in the RAM180 and performs various types of processing according to the loadedvarious types of data. The image processing process 180 a includesprocessing performed by the function units represented in FIG. 1, 8 or10, e.g., the processing illustrated in FIG. 7, 9 or 11. All theprocessing units virtually implemented in the CPU 150 do not necessarilyrun on the CPU 150, and it suffices if only processing units needed forprocessing are virtually implemented.

The above-described image processing program 170 a is not necessarilystored in the HDD 170 or the ROM 160 from the beginning. For example,each program may be stored in a “portable physical medium”, such as anFD, a CD-ROM, a DVD disk, an magneto-optical disk, or an IC card. Thecomputer 100 may acquire each program from the portable physical mediumand execute the program. Alternatively, each program may be stored inanother computer, or a server device, connected to the computer 100 viaa public line, the Internet, a LAN, or a WAN and the computer 100 mayacquire each program from the computer or the server device and executethe program.

It is possible to improve the accuracy of authentication.

All examples and conditional language recited herein are intended forpedagogical purposes of aiding the reader in understanding the inventionand the concepts contributed by the inventor to further the art, and arenot to be construed as limitations to such specifically recited examplesand conditions, nor does the organization of such examples in thespecification relate to a showing of the superiority and inferiority ofthe invention. Although the embodiments of the present invention havebeen described in detail, it should be understood that the variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A non-transitory computer readable recordingmedium having stored therein an image processing program that causes aninformation terminal to execute a process comprising: acquiring an imageof a first subject that is captured by a first sensor provided on a backsurface of a surface on which a screen of the information terminal isdisposed; and when displaying the image on the screen, changing a degreeof scaling up/down of the image and a position at which the image isdisplayed in accordance with a position of a second subject that isimaged by a second sensor provided to the information terminal.
 2. Thecomputer readable recording medium according to claim 1, wherein theprocess further comprises: by using a distance sensor that measures adistance, measuring a distance between the information terminal and thesecond subject; and detecting the position of the second subject fromthe distance between the information terminal and the second subject. 3.The computer readable recording medium according to claim 1, wherein theprocess further comprises: by using a distance between characteristicpoints of a face acquired from an image of a face of a user of theinformation terminal captured by the second sensor, estimating adistance between the information terminal and the face of the user ofthe information terminal; and estimating the position of the secondsubject from the distance between the information terminal and the faceof the user of the information terminal.
 4. The computer readablerecording medium according to claim 1, wherein the process furthercomprises: by using a size of the living body of a user of theinformation terminal acquired from the image captured by the firstsensor, estimating a distance between the information terminal and aface of the user of the information terminal; and estimating theposition of the second subject from the distance between the informationterminal and the face of the user of the information terminal.
 5. Animage processing method comprising: acquiring, by a processor, an imageof a first subject that is captured by a first sensor provided on a backsurface of a surface on which a screen of the information terminal isdisposed; and when displaying the image on the screen, changing, by theprocessor, a degree of scaling up/down of the image and a position atwhich the image is displayed in accordance with a position of a secondsubject that is imaged by a second sensor provided to the informationterminal.
 6. The image processing method according to claim 5, furthercomprising: by using a distance sensor that measures a distance,measuring, by the processor, a distance between the information terminaland the second subject; and detecting, by the processor, the position ofthe second subject from the distance between the information terminaland the second subject.
 7. The image processing method according toclaim 5, further comprising: by using a distance between characteristicpoints of a face acquired from an image of a face of a user of theinformation terminal captured by the second sensor, estimating, by theprocessor, a distance between the information terminal and the face ofthe user of the information terminal; and estimating, by the processor,the position of the second subject from the distance between theinformation terminal and the face of the user of the informationterminal.
 8. The image processing program according to claim 5, furthercomprising: by using a size of the living body of a user of theinformation terminal acquired from the image captured by the firstsensor, estimating, by the processor, a distance between the informationterminal and a face of the user of the information terminal; andestimating, by the processor, the position of the second subject fromthe distance between the information terminal and the face of the userof the information terminal.
 9. An information terminal comprising: aprocessor that executes a process comprising: acquiring an image of afirst subject that is captured by a first sensor provided on a backsurface of a surface on which a screen of the information terminal isdisposed; and when displaying the image on the screen, changing a degreeof scaling up/down of the image and a position at which the image isdisplayed in accordance with a position of a second subject that isimaged by a second sensor provided to the information terminal.
 10. Theinformation terminal according to claim 9, the process furthercomprises: by using a distance sensor that measures a distance,measuring a distance between the information terminal and the secondsubject; and detecting the position of the second subject from thedistance between the information terminal and the second subject. 11.The information terminal according to claim 9, the process furthercomprises: by using a distance between characteristic points of a faceacquired from an image of a face of a user of the information terminalcaptured by the second sensor, estimating a distance between theinformation terminal and the face of the user of the informationterminal; and estimating the position of the second subject from thedistance between the information terminal and the face of the user ofthe information terminal.
 12. The information terminal according toclaim 9, the process further comprises: by using a size of the livingbody of a user of the information terminal acquired from the imagecaptured by the first sensor, estimating a distance between theinformation terminal and a face of the user of the information terminal;and estimating the position of the second subject from the distancebetween the information terminal and the face of the user of theinformation terminal.